1. Field of the Invention
In view of these considerations it is the objective of the present invention to provide a power-assisted steering system with a steering damper in which the steering damper has a simpler configuration with regard to the constructional elements used and is less complicated to assemble.
2. Discussion of Related Art
This objective is met by a power-assisted steering system with the with the features described in the detaileed description of the invention. The large N sealing area entailed by this arrangement requires a 100% quality test at the end of the manufacturing process.
Because the one or more steering dampers are arranged in the hydraulic line, the sealing of the hydraulic damper in the assembled position is reduced ultimately to the sealing of a simple line. Fluid-tightness at this point is very easy to achieve. The steering damper itself can be simply constructed using this arrangement.
If, in addition, the hydraulic line is made of a metal and the steering damper is arranged in an expanded section of the hydraulic line, the fixing of the steering damper in the line is especially simple. In particular, it can also be located floatingly in this position. Assembly can further be made especially simple by making the expanded portion of the hydraulic line separable, for example, in the manner of a plug connector, the expanded portion being opened for assembly of the steering damper and closed pressure-tight after assembly. For this purpose bonding or screw fixing can be provided, as can a clamped joint.
If the steering damper has a basic body which is arranged movably along a path in a working chamber and delimits with an outer wall of the working chamber a first channel through which hydraulic fluid can flow, the steering damper with its housing can be located in the working chamber without the housing itself forming a sealed face to the outside. If at one end of the travel of the basic body oriented away from the associated cylinder, the basic body so abuts against a valve seat that the first channel is closed in the return flow direction oriented away from the cylinder, and in particular if the basic body of the steering damper forms the valve element of a non-return valve, the diversity of parts can be further reduced.
In this case the basic body is preferably preloaded by a spring in the position which closes the channel. and opens the first channel when fluid flows in the main flow direction oriented towards the cylinder of the power-assisted steering system. Inside the housing a second inner channel can be provided, which is closable by a spring-loaded valve element, this valve element opening when subjected to pressure in the return flow direction and closing in the main flow direction. In this way the characteristics of a damping valve are realised in a simple fashion inside the basic body.
The effect of the steering damper can be made temperature-dependent if the spring of the valve element is made of a shape memory material. In addition, the basic body can have a number of flat faces on its outer surface, which faces form the first channel with a relatively large cross section in an especially simple way.
An especially simple arrangement of the steering damper results if a steering damper is mounted floatingly in each hydraulic line. In this case the working chamber of the steering damper can be arranged in the end portion of the hydraulic line.
In a different embodiment, in which the fluid flow is controlled by a throttle element, the steering damper has a tubular damper housing which has a guide element arranged in the housing, a throttle element displaceable in the main flow direction or in the return flow direction being mounted on the guide element. The throttle element can be preloaded by a spring in the return flow direction. The housing preferably has a stepped internal bore with one larger internal diameter and at least one smaller internal diameter, the throttle element being forced against the spring pressure into the zone of larger internal diameter during operation when fluid flows in the main flow direction, thus delimiting a larger free cross section with the bore, whereas it delimits a smaller free cross section when fluid flows in the return flow direction. Finally, the guide element in this embodiment can be located preferably coaxially in the bore by a fixing section which has recesses or flat portions. In this way it is ensured firstly that the guide element is arranged in a favourable position with regard to flow and secondly it does not constrict the necessary free cross section.
In the following description one example of the present invention is described with reference to the drawings.